I have a Waterfurnace Premier 2 4.5 ton geothermal system that was installed in 1997. So far I've replaced the main condenser coil, the pumping unit (twice), the main system board, and various other electonics.

The other day I found out that the condenser coil has another hole in it and it's going to cost several thousand dollars to fix.

I've had several estimates on repairs but most installers are recommending that I replace the unit. I'm trying to decide if I should replace it with a new geothermal unit or go with a high efficiency air to air heat pump instead.

So far I'm looking at Bosch and Waterfurnace for the geothermal and the Carrier greenspeed for air to air. Does anyone have any suggestions?

The air to air units seem to have the advantage of simplicity, which would mean fewer repairs and a longer operating life but they are lower efficiency (13-14 eer vs. 23+ for geothermal). It's hard to say exactly how much that extra efficiency will be worth in the long run.

The geothermal units have the advantage of higher efficiency but they're pricier, more complex, seem to have a much shorter life-span and may cost more to operate. But since I already have the ground loop the difference isn't quite so big and there's a 30% tax credit to take into account. They can also be used to pre-heat water for the hot water heater.

So, what should I do?